For years Britain has had not one annual budget but two. The real deal – the one where the chancellor stands outside 11 Downing Street with his little red box – has been in the spring, but there has also been another round of tax and spending measures included in an autumn statement.

Philip Hammond has changed all that. As of now, there will be only one big set-piece event each year and it will be a budget in the late autumn. This week we will see the first spring statement, a pared-down affair in which the chancellor will provide the latest economic and public finance forecasts from the Office for Budget Responsibility, announce some areas for consultation and leave it at that. No tax sweeteners, no extra money for cabinet colleagues pleading for cash, no change to the government’s deficit-reduction approach.

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Hammond made it clear on the BBC’s Andrew Marr Show that he doesn’t want the spring statement to create too many waves, and there are both political and economic reasons for adopting such an approach. It is less than a year since the last election and unless forced to do so chancellors don’t give money away early in a parliament even if it means alienating voters as a result. As it happens, the polls are not looking too bad for the Conservatives.

Hammond certainly has the scope to be generous should he wish to be. Although it is less than four months since the last OBR update on the economy, there have been three developments worthy of note – all of them helpful to the chancellor.

Firstly, growth in 2017 – while sluggish – has come in above the OBR’s November forecast of 1.5%. An upgrade to the 1.4% predicted for 2018 also looks likely.

Secondly, the public finances look a lot better or, to be more accurate, much less bad than expected last autumn. Back then the OBR was assuming a budget deficit of just shy of £50bn in the current financial year: the actual figure looks like being closer to £40bn. For the first time since the financial crisis, tax receipts are covering day-to-day government spending, which means the Treasury is only borrowing for investment.

Quick Guide

What is austerity?

What is austerity?

Austerity is how governments across Europe – from the UK to Greece – tried to clear the overdrafts, or deficits, they racked up in the wake of the great financial crisis.

How did governments try to achieve this?

Their strategy was two-fold. First, cut spending on the public sector, on wages, for instance, or on social security. Second, raise revenue through higher taxes and selling state assets. Greece, for instance, has sold its airports in Corfu and Santorini, among others, to a German company.

What was their reasoning?

Proponents made a variety of arguments for this strategy. It was said that governments had spent too much money, that everyone needed to tighten their belts. The UK’s then-chancellor, George Osborne, claimed that the public sector was "crowding out" the private sector, taking resources and workers away from businesses. Particularly influential was a paper by two US-based economists, Ken Rogoff and Carmen Reinhart, arguing that once a country’s total public borrowing rose above 90% of its national income, or GDP, growth would slow sharply.

Did austerity get unanimous backing?

Critics argued that austerity would stop economies recovering from the shock of the banking meltdown and would make teachers and nurses and people with disabilities pay for the excesses of bankers and chief executives. In his book Austerity: The History of a Dangerous Idea, political economist Mark Blyth showed that austerity had been tried before in the 20th century – everywhere from Weimar Germany to 1930s America – and failed, often with politically disastrous consequences.

Finally, no sooner had the OBR slashed its forecasts for productivity than the numbers started to improve, with the final two quarters of 2017 recording output per head rising by 0.8-0.9%. While it is far too early to draw any hard conclusions from such limited data, it is possible the OBR has been a little too gloomy about the long-term productivity outlook.

What is gross domestic product (GDP)?

Gross domestic product (GDP) is a key government statistic and provides a measure of the UK's total economic activity.

Put simply, if GDP is up on the previous three months, the economy is growing; if it is down, it is contracting. Two or more consecutive quarters of contraction mean the economy is officially in recession.

GDP is the sum of all goods and services produced in the economy, including the service sector, manufacturing, construction, energy, agriculture and government.

Economists are concerned with the real rate of change of GDP, which shows how the economy is performing once inflation is taken into account.

The Office for National Statistics produces quarterly official GDP figures about three and a half weeks after the end of each three-month period.

The ONS uses three measures and they should, at least in theory, all add up to the same number.• The value of all goods and services produced - known as the output or production measure.• The value of the income generated from company profits and wages - known as the income measure.• The value of goods and services purchased by households, government, business (in terms of investment in machinery and buildings) and from overseas - known as the expenditure measure.

The ONS publishes three estimates of quarterly GDP figures. The first "flash" estimate comes out about 25 days after the quarter in question has ended. The figures usually get revised in subsequent months as more data from businesses and government departments is received. But even the third, dubbed "final", estimate of quarterly GDP is not set in stone: the Blue Book, which is published once a year, in August, contains revisions going back the last 18 years.

The National Institute of Economic and Social Research's estimate comes out about three weeks before the official figures.

The ONS also calculates the size of the UK economy relative to the number of people living here. GDP-per-capita shows whether we are actually getting richer or poorer, by stripping out the impact of population changes.

Finally, of course, there’s the little matter of Brexit, now little more than a year away. All things considered, the government has been pleasantly surprised by how well the economy has held up since the referendum but accepts that there could be more difficult times ahead. It thinks the economy might be more of need of support in 2019 than it is in 2018.

Labour would prefer a bolder approach. The shadow chancellor, John McDonnell, says that austerity has been holding growth back – an argument backed by the OBR. There is no doubt that the economy would have expanded faster had it not been for the curbs on departmental spending, welfare cuts and tax increases implemented since 2010.

Nor is at all obvious that the pain inflicted has been worth it. In a report published last week, the Washington-based Center for Economic and Policy Research thinktank notes that the financial markets have not been troubled by the UK’s rising national debt, with the interest rate on 10-year government borrowing below 1.5%.

“This is significantly lower than the current rate and projected rate of inflation, which means that the UK government can borrow long-term at real interest rates that are negative. Since there are many public investments that have a positive real rate of return by increasing productivity, this means the economy and the public could benefit from public investment financed at these long-term negative real interest rates.”

Higher investment spending makes a lot of sense. For a start, it would help offset higher interest rates from the Bank of England. It would also provide a much-needed boost to the UK’s struggling construction sector. It would help address the problem of weak long-term productivity growth identified by the OBR. And it would raise activity in the short term, putting the UK in a stronger bargaining position in the Brexit negotiations.

Hammond is in a much stronger position personally than he was a few months ago. He will be able to brush aside suggestions that he could find better uses for his £10bn windfall this year than save it for a rainy day.

But the case for higher investment is being made not just by Labour but also by Hammond’s critics within the Conservative party, such as the MP Nick Boles and Theresa May’s former policy adviser Nick Timothy.

They note that violence in prisons is on the increase and that waiting lists in A&E departments of hospitals are rising sharply. After eight years of austerity, public services are close to breaking point.